Understanding Metering in Photography with Nikon D90

Metering is to calculate the optimal exposure from the light source for the subject you are shooting. Back in old days, photographers used to rely on external light metering device because cameras were not equipped with the sensor that can measure the sensitivity of light and give you information about exposure settings. But today, every modern DSLR cameras come with sensor that meters the light entering the camera sensor and determines correct exposure settings for you. Even though some DSLR brand uses different naming convention for metering mode, overall idea of metering system is same. For this article, I will be taking reference of Nikon D90 to explain different metering modes available in modern DSLRs but this technique implies for all DSLR though.

What is Metering mode?

Metering mode is different exposure mode available in your camera settings. Metering mode is used to deal with correct exposure for your subject. It is mainly used when there is challenging lighting condition (too dark or too bright or combination of both).

When you frame your subject, it determines the intensity of light coming into the sensor and give that information to the light meter. Most of the time camera does good job but sometimes it gets deceived by the light source when there is a mixture of dark and bright light source. If you are shooting in Auto mode, camera tries to set the correct exposure automatically by calculating correct combination of shutter speed and aperture size (F-stop) and different other parameters (which we discuss later in this post) . Like I said before, it works perfect most of the time unless there is serious lighting condition like sunset with dark sky and bright horizon, subject under very bright sunlight etc.

I hope you understood the idea of Metering and when to use it. Now lets talk about different types of Metering mode available in modern DSLR cameras.

There are three common Metering Modes available in almost every DSLRs and they are :

1. Matrix Metering2. Center-Weighted Metering3. Spot Metering

1. Matrix Metering

Nikon D90 uses different Matrix metering depending up on type of the lens you are using. It uses 3D Color matrix metering II ( with type G and D lenses); Color matrix metering II (with other CPU lenses). This is the default setting for D90. When you look at the LCD screen on the top of D90 body (on the right side where shutter release button is), Matrix metering mode is indicated by black rectangle shape with the dot in the middle.

While metering using Matrix metering mode, camera divides entire frame into multiple zones and calculate exposure based up on colors of light, distance of the subject, color tones etc. Camera collects information from all the zones but gives priority on that area where you put your focus on (inside the frame). Matrix metering mode does pretty good job most of the time and should be used for day to day photography.

2. Center-Weighted Metering

Center-Weighted metering mode is represented by little circle with a central dot inside. Like in the Matrix metering mode, it also calculates exposure from the entire frame but the center area is given more priority (weight) during calculation. As per Nikon website, It gives weight of 75% to 6, 8, or 10-mm circle in center of the frame. As name suggests, Center-Weighted metering mode doesn’t rely on your focused area but gives priority to the center of the frame instead. It is not recommended setting for most of the time and also considered as least accurate metering method to use daily. It should only be used when you want to emphasize center of the frame.

3. Spot Metering

Inside LCD screen, Spot metering mode is indicated by little circular dot. Unlike other two methods, while metering light, it only gives priority on small area where your focus point is and ignores everything else inside the frame. As per Nikon website, it meters 3.5mm circle (about 2% of the frame) centered on active focus area. It is widely used when you want to give proper exposure to your focused area no matter how surrounding will be.

How to change Metering modes?

It depends on camera brands and model but in Nikon D90, there is a dedicated button left to the shutter release button. When you press that button and rotate rear command dial, it switches metering mode from one to another.

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Comments

I am new to photography.
As I understand, exposure is controlled by shutter speed, aperture and ISO settings. Metering would determine the amount of light incident on the sensor which in itself is controlled by the above. If I use the manual setting to control all three ( shutter speed, aperture and ISO ), why do I need to manipulate the metering – what difference will it make to use the metering.

Samir,
I agree with you that exposure is controlled by Shutter speed, Aperture and ISO settings and sometimes it is also refereed as Exposure Triangle. But aside from that Metering is used by camera to let know sensor that how much light is present. And after camera’s metering system senses lighting environment, you may need to use any settings (like Shutter speed, Aperture or ISO value) you familiar with to set proper exposure. Actually Metering will help to determine which area of your subject should give priority while calculating proper exposure.

Sorry to take this further, Umesh.
But isnt metering a way to analyse the amount of reflected light which helps the camera to adjust the shutter speed ,aperture and ISO automatically to obtain an appropriate image on the sensor ? If I am right, my question is, why do I need to meter when I am manually choosing the shutter speed, aperture and ISO setting. I cant seem to find a logical answer. Apologies for drilling in deep, but I have recently bought a D5000 and am in the learning phase ( I used to own a 3 mega pixel point and shoot camera 3 months back ) and hence the queries. I have a lot to ask, but it will be one at a time.
Thank you for all your posts.
They have been extremely useful.
Can you also post something on ‘understanding D lighting and white balance’

That’s the point. When you are saying you are using “Manual mode”, that means you are controlling everything manually. When you dial into Manual mode, camera will gather information about how much ambient light is present in the environment and then based up on that information, you will have to set your camera Shutter speed, Aperture or ISO value to balance proper exposure. Manual mode means you are controlling your camera completely.

For example if you are shooting in Aperture priority mode, then your camera meters the light and adjusts certain Shutter speed for correct exposure and if you are shooting in Shutter priority mode, camera automatically gives you proper Aperture value for correct exposure. These are semi-auto mode where camera does little bit for you and you have to do little bit to set correct exposure. I hope it helps.

Also FYI, I have several posts about Active D-Lighting and White Balance. Please use search bar on the top right corner and use your keyword. I am sure you will find it.

I am not sure if this blog is still active or will be responded, nevertheless I will give it a try.

One question, when you mention that in Centre-Weighted & Spot Metering mode the Camera will only focus expposure on the centre of the frame, does that mean I have always focus the subject in the centre circle.

What I mean is for eg. if I use single point focus with spot metering and the point of focus in my frame is NOT the centre (it is somewhere else) will the camera still use the centre of the frame for exposure.

Untill now I was of the impression that if I use single point focus and set spot metering it would pick exposure from that zone in the frame.

Hi Cherag,
Sorry for the confusion. In spot metering, I did say key point is where the active focus area is but in Center-weighted metering system, no matter where you focus, metering system will give priority to the Center of the frame. Center-weighted metering should not be used very often and should only be used if you want to prioritize center of the frame.

I will be editing this post and try to remove those confusion you had.

This does clear a bit of my confusion, I used spot metering with single point focus on my recent wild life photography trip, this setting helps when you have the subject sitting far away in the bushes and you want to avoid the camera focusing on additonal elements in the frame.

I must say I just about happened to come across this site today and am massively impressed with the information provided.

Thank you Cherag for your appreciation. Sometimes I write article, it gets old and if there are some mistakes or confusion, I won’t get chance to correct them until somebody points out.

Like you mentioned in your comment, Spot metering is very much famous in wild life photography where you want to focus on particular subject while ignoring other parts.

Currently, I am working on integrating forum inside this blog where visitors can sign up for free and post their questions, reply to others and message other members of community. They can even share their photos by uploading to our sever or linking from external source like flickr. I hope you will join our community and share your work and ideas.

I will be more than happy to be part of the forum whenever time permits and contribute with whatever limited knowledge i have acquired (I must warn you I have been introduced to D-SLR photography since the past approx 4yrs) and am still learning the tricks of the trade.

I am confused by two things, spot metering and autofocus single point. The spot metering will meter off the middle of the frame. How does it work if I use spot metering and want to choose single point to focus something at the corner? I usually use manual mode.

When you use spot metering, it always choose the focus point for metering. Let’s say you use manual mode, use single point focusing mode and used spot metering, and you selected the corner area, it always picks the light in that particular spot and do the metering unlike center-weighted metering mode which always calculates based on center of the frame.

Thank you so much, Umesh. I have one more question. I know the difference between DX and FX from theory. But can you really tell the difference from the DX pictures to FX pictures? I am debating if I should upgrade my camera.

If budget is not a problem, I will advise you to go for FX. Personally, I feel FX performs better in low light condition. It has wide variety of lenses which offers sharp and clear pictures and also has wider dynamic range which helps capturing wide range of colors.